Geographos is classified as an Earth-crossing
asteroid because its orbit
can evolve to intersect Earth's orbit.
Scientists have found fewer than 300 Earth-crossing
asteroids; however, they believe hundreds of thousands of
objects might exist. The asteroids probably include several
hundred objects larger than Geographos, thousands larger than
half a mile across, and a few hundred thousand that are larger
than a football field.

Geographos is an irregular body with dimensions of about 5.1 kilometers
by 1.8 kilometers (3.2 miles by 1.2 miles). It has
the largest length-to-width ratio of any solar system object ever
imaged to date. Scientists do not know whether the asteroid is a single
coherent body or consists of several distinct pieces. Geographos
was discovered at Palomar Observatory near San Diego, California, in
1951. The asteroid's name, which means geographer, was chosen to
honor the National Geographic Society for its support of the
Palomar Mountain Sky Survey.

The above image shows the outline of asteroid Geographos viewed
from above its north pole. Researchers obtained radar images of
the asteroid on August 30, 1994, when the asteroid was 7.2 million
kilometers (4.5 million miles) from Earth. They used a planetary radar
instrument to image the asteroid from the Deep Space
Network's facility at Goldstone, California.
The tick marks on the
borders are 1 kilometer apart. The central white pixel locates the
asteroid's pole. The gray scale is arbitrary and no meaning is
attached to brightness variations inside the silhouette.
Scientists conducted the radar observations a few days after
Geographos passed 5 million kilometers (3.1 million miles) from
Earth, its closest approach in at least two centuries.
(Courtesy Dr. Steven J. Ostro, JPL/NASA).